Cooling and Warming Effects on Cold Hardiness Estimations of Three Woody Ornamental Taxa

Abstract

<jats:p>Cooling treatments of 2, 4, and 6C/hour or warming at 25, 4, or 0C influenced the cold hardiness estimates of x <jats:italic>Cupressocyparis leylandii</jats:italic> (A.B. Jacks. and Dallim.) Dallim. and A.B. Jacks. (Leyland cypress), <jats:italic>Lagerstroemia indica</jats:italic> L. (crape myrtle), and <jats:italic>Photinia ×fraseri</jats:italic> Dress `Birmingham' (redtip photinia) at four times during the year. New growth from all taxa, especially spring growth, was injured or killed at higher temperatures by the fastest cooling rate and/or by warming at 25C. Cold hardiness of Leyland cypress was unaffected by the cooling and warming treatments. Crape myrtle had a significantly higher lowest survival temperature (LST) when warmed at 25C than at 4 or 0C. Photinia leaves and stems cooled at 6C/hour or warmed at 25C generally resulted in a higher LST than those cooled more slowly or warmed at lower temperatures. Cooling rates of 14C/hour and warming at 0 to 4C should be used in freeze tests with Leyland cypress and crape myrtle. For leaves and stems of photinia, 2C/hour cooling and warming at 0 to 4C should be used.</jats:p>

How Pretest Temperatures Change the Cold Hardiness of Grapevine (Vitis ViniferaL. Cv. Karaerik) Dormant Buds?

“…The dependence of the rise in deadly temperature caused by rapid cooling on a plant frost tolerance agrees with the findings of Haynes et al (1992). When plant tissues were submitted to rapid freezing, damage resulting from cell interior freezing may occur at higher temperatures where the rate of diffusion of water from the intracellular could not keep pace with the rate of temperature decrease (Levitt, 1980).…”

Survival of Water-stressed Rhododendron Subjected to Freezing at Fast or Slow Cooling Rates

“…Whether freezing injury of even less cold-hardy plants remains unaffected by cooling rate cannot be inferred from our data. The dependence of the increase in lethal temperature caused by rapid cooling on a plant's cold hardiness agrees with the findings of Haynes et al (1992). These authors reported 2.5 to 3C difference in cold hardiness of crape myrtle (Lagerstroemia indica L.) stems cooled at 2 and 6C/h in January and March, but they did not detect significant differences between slow and fast cooling in October and August when plants were less cold hardy.…”

“…Sample temperature was recorded by thermocouples placed next to the stem or leaf. To avoid excessive supercooling of tissue water, when the temperature of the samples stabilized overnight at -2.0 ± 0.5C, the samples Rapid cooling may increase the degree of freezing injury in plants (Chen and Gusta, 1978;Havis, 1964;Haynes et al, 1992;Krasavtsev, 1973;Levitt, 1980;Slater and Warmund, 1986;Steffen et al, 1989;Warrington and Jackson, 1981;White and Weiser, 1964). Freezing plants >5C/h has been classified as rapid cooling (Levitt, 1980).…”

Logit Models for Estimating Lethal Temperatures in Apple

“…Resistance indices, such as the temperature at 50% lethality (LT 50 ) (Levitt, 1972), the lowest survival temperature (LST) (Quamme et al, 1972), or the temperature interval between 10% and 90% injury (Ketchie et al, 1972), are desirable in studying the acclimation-deacclimation process or the effects of environmental stimuli on the degree of frost resistance. However, in many cases, the resistance indices are estimated graphically from temperature curves (e.g., Haynes et al, 1992;Montano et al, 1987;Ritchie et al, 1985). The shortcomings of these graphic methods are that there is an inclination to subjective bias errors, only rough estimates are produced, and the degree of confidence associated with the resistance index cannot be estimated.…”